The Effects Of Volatile Anesthetics And Neuromuscular Blockade On Transcranial Electrical Motor Evoked Potentials

Objective To develop the optimal monitor method of intra- operative transcranial electrical motor evoked potentials(MEPs) based on different stimulation patterns and record muscles. Then to compare the effects of three volatile anesthetics and neuromuscular blockade on MEPs based on optimal MEPs monitor method.Methods①Eighteen ASAⅠ-Ⅱpatients aged 23-64 years undergoing craniotomy were enrolled. Stimulation patterns (100-500 V,100-1000 Hz,2-6 stimuli) were varied randomly while propofol and remifentanil were administered at a constant rate. The amplitude and latency were recorded by abductor pollicis brevis musle. Repeated Measures Anova tests was used to investigate the effects of Stimulation patterns on MEPs.②Twenty ASAⅠ-Ⅱpatients aged 23-62 years undergoing craniotomy were enrolled. Triangular muscle, biceps brachii muscle, triceps brachii muscle, brachioradialis muscle, extensor digitorum communis muscle, abductor pollicis brevis, abductor digiti minimi muscle, rectus femoris muscle, tibialis anterior muscle, gastrocnemius muscle and abductor hallucis were selected for MEPs recording. Sevoflurane was introduced at 0.5,0.75,1.0 and then 1.0 MAC (15 minutes each), and the effects on MEPs were studied.③Sixty ASAⅠ-Ⅱpatients aged 18-65 years undergoing craniotomy were randomly assigned to 3 equal groups receiving sevoflurane, isoflurane and desflurane. Volatile anesthetics were introduced at 0.5, 0.75,1.0 and then 1.3 MAC (15 minutes each) during 6 stimuli delivered at 1000 Hz and 300 V, the amplitude and latency of MEPs were recorded by abductor pollicis brevis muscle, and the effects of three volatile anesthetics on MEPs were studied. The bispectral index (BIS) was simultaneous recorded at different MAC, and the correlation between BIS and MEPs was investigated.④Twenty ASAⅠ-Ⅱpatients aged 22-65 years undergoing craniotomy were enrolled. Optimal MEPs monitor method was used to record the amplitude and latency of MEPs at TOF 0,1,2 and 4, respectively.Results①Maximum MEP amplitude and recording success rate were observed during 6 stimuli delivered at 1000 Hz and 300 V.②Maximum MEP amplitude were observed at abductor pollicis brevis muscle in upper limb and abductor hallucis muscle in lower limb at baseline and 0.5-1.3 MAC.③The MEPs amplitude was decreased and latency was increased in a dose-dependent manner (P<0.05). The success rates of MEP recording were 100% during administration of 0.5-0.75 MAC sevoflurane, isoflurane and desflurane, respectively. Up to 1.0 MAC, the success rates were 100%,95% and 80%,respectively. Up to 1.3 MAC the success rates were reduced to 95%,80% and 55%,respectively. The MEPs amplitudes during the administration of 0.75-1.3 MAC were no significant difference among sevoflurane, isoflurane and desflurane group. The MEPs latency observed during the administration of 0.5-1.3 MAC in sevoflurane and isoflurane group were significantly lower than desflurane group.The positive correlation was observed between MEPs amplitudes and BIS of sevoflurane, isoflurane and desflurane.④The MEPs were recorded successfully at TOF 0,1,2 and 4, respectively. The MEPs amplitudes were significantly decreased as the degree of neuromuscular blockade increased (F=12.487,P=0.000)Conclusion①Desflurane has greater suppressive effect on MEPs than either sevoflurane or isoflurane.1.0 MAC of either sevoflurane or isoflurane, and 0.75～1.0 MAC of desflurane may be suitable for MEPs monitoring.②The MEPs can be successfully monitored at TOF 0 based on the optimal MEPs monitor method.,...